Peptide Therapeutics: Unveiling the Potential against Cancer—A Journey through 1989.

Simple Summary: The extraordinary growth in the global pharmaceutical industry has extended to include peptides, which are amino acids linked together with an amide bond. Due to their well-tolerable safety profile and specificity, therapeutic peptides offer a means to address unmet medical challenges. A well-known example of a commonly administered peptide is insulin. Peptides are considered excellent complements and, in some cases, preferable alternatives to both small molecules such as paracetamol and very large antibodies. At present, around 100 peptide drugs are available on the global market, with ongoing research yielding over 150 peptides in clinical development and an additional 400–600 peptides undergoing preclinical studies. Peptides play a crucial role in cancer research and treatment, and they can be involved in various aspects of cancer development, detection, and treatment. These medicines demonstrate exceptional efficacy in combating cancer, contributing to improved survival rates for cancer patients. The United States Food and Drug Administration (FDA) has approved a plethora of peptide-based drugs as effective drugs in cancer therapy. Peptides possess high specificity, permeability, target engagement, and a tolerable safety profile. They exhibit selective binding with cell surface receptors and proteins, functioning as agonists or antagonists. They also serve as imaging agents for diagnostic applications or can serve a dual-purpose as both diagnostic and therapeutic (theragnostic) agents. Therefore, they have been exploited in various forms, including linkers, peptide conjugates, and payloads. In this review, the FDA-approved prostate-specific membrane antigen (PSMA) peptide antagonists, peptide receptor radionuclide therapy (PRRT), somatostatin analogs, antibody–drug conjugates (ADCs), gonadotropin-releasing hormone (GnRH) analogs, and other peptide-based anticancer drugs are analyzed in terms of their chemical structures and properties, therapeutic targets and mechanisms of action, development journey, administration routes, and side effects. [ABSTRACT FROM AUTHOR]